Abstract

Motivated in part by the Snowden revelations, we address the question of
whether intelligence and law-enforcement agencies can gather actionable,
relevant information about unknown electronic targets without conducting
dragnet surveillance. We formulate principles that we believe effective, lawful
surveillance protocols should adhere to in an era of big data and global
communication networks. We then focus on intersection of cell-tower dumps, a
specific surveillance operation that the FBI has used effectively. As a case
study, we present a system that computes such intersections in a
privacy-preserving, accountable fashion. Preliminary experiments indicate that
such a system could be efficient and usable, suggesting that privacy and
accountability need not be barriers to effective intelligence gathering.

This work was supported in part by the National Science Foundation under grant
1016875, the Office of Naval Research under grant N00014-12-1-0478, the
Defense Advanced Research Projects Agency (DARPA) and the Air Force Research
Laboratory under contract FA8750-13-2-0058, and DARPA and SPAWAR Systems Center
Pacific under contract N66001-11-C-4018.
The views and conclusions herein are those of the authors and should not be
interpreted as necessarily representing the office policies or endorsements,
either expressed or implied, of DARPA or the U.S. Government.